The field of the present invention is gas detection and particularly gas detection determined by ion mobility range segregation.
Historically, gas detection utilizing ion molecule reactions and subsequent detection of the resulting analyte ions by their differing ion mobilities have been accomplished by two different detection methods. In each method, the reactant ions, formed by a variety of techniques, undergo ion molecule reactions with the sample molecules whereby stable positive or negative product ions are produced. These detection methods for the product ions are:
(1) Plasma chromatography. Here, ion identification is achieved by selective ion gating followed by statistical analysis of the time required for the ions to reach a collector. Since different ions have different mobilities in the presence of an electric field, the collection time can be used for ion identification.
(2) Detection by diffusion. Here, ions are contained in a constant flow stream, and travel through a complex geometric labyrinth in which they are separated by radial diffusion and subsequent neutralization before reaching the collector. The larger product ions which are able to reach the collector before neutralization are detected.
These prior methods are limited in practicability in that their functional use requires complex geometries for each type of ion requiring detection or complex time base data collection techniques and analysis for mobility identification.